Creating Curves on CNC Equipment

Instructions for cutting curved shapes can be hand-programmed, but it makes more sense to draw in CAD and import the shapes to the CNC controller. October 26, 2005

I am interested in making some new programs for the Weeke CNC machine at our factory. I am having a little trouble using WoodWOP 4.5 when designing worktops, etc with curves or arcs. For instance, looking at an example on our machine, making an oval top is a complicated mess of SINE and COSINE rules to plot out the points. Surely you don't need a degree in mathematics to design these shapes?

I notice some people are using AutoCAD 2000 or similar to design shapes. Would this make my life easier? If so, I may get the company to purchase AutoCAD.

Forum Responses
(CNC Forum)
From contributor B:
I never could understand why some CNC manufacturers send out machines without guidance on using drawing programs such as AutoCAD and G-code CAM software to create code. Nothing could be more accurate and simpler. It just makes no sense to me to write code when CAM software will take your CAD drawing and generate the code.

Any CAD program that will output a .dxf file will work, as that is what the CAM packages I know of import. I use Enroute 3 Pro for my CAM work, but there are many other programs out there in that and lower price ranges.

If there is someone that can explain to me an advantage of writing code versus using CAD and CAM software, I would love to learn the reasons.

From contributor M:
From what I know of Weeke machines, you don't need the full version of Autocad for 2D shapes. You can get by with any version of Autocad Lite. In order for Woodwop to import a dxf, you must assign the geometry to specific layers that should be part of the machine documentation. You will probably have trouble with ellipses and splines, but there are workarounds for that. I am in the same corner as the contributor above. I don't think the customer is well served when a distributor sells a machine without a reasonable CAM package included. Everyone makes their fair share of rectangles, but the machines exist because of their ability to cut arcs on multiple planes.

From contributor C:
As a matter of fact, you do almost need a degree in mathematics to program in arcs and ellipticals.

We use Autocad 2004 to draw everything up. This makes life much easier. You will have to get CAD, and you will also have to contact Stiles Machinery to get a copy of the BPP software from them. It's a go between software. You assign layers in CAD, and then run the dxf file through the converter. It takes some getting used to, but makes life much easier when dealing with WoodWOP.

From the original questioner:
Thanks a lot for the responses. In the end, I managed to find an ellipse that came with the software installation and butchered that file to change the dimensions and then rewrite it so it did the oval in quarters. The reason is that our bed is only capable of working on a piece 3000 x 1500 (or 10' x 5' if you prefer) and the top was 3200 x 2200!

So basically, my best option (for creating 2D shapes at the minimum) is to get some kind of CAD package that will output dxf files and when imported, the drawings will automatically have the counters' starts/ends/rads/etc entered for me?

Yes, the support for the machine is rather limited. I think the plan was only initially to do basic squares/oblongs/rectangles, etc, which is a terrible waste of such a machine! I'm assuming, working in 3D in a CAD package, I could create embossing and chamfers with nice angles on a lot easier.

I am basically a beginner, having only had experience programming simple items on a CNC lathe for metal work and having to manually program it line by line years ago. Also, I've read that v5.0 of WoodWOP is not available. Is this a free upgrade or will Homag want lots of money from us to upgrade? What will I gain?

From contributor G:
Contributor B, maybe because it's faster in some instances. The questioner's example program is created to make ovals different sizes by changing overall size (same major and minor axis) or making different size and shape ovals by changing overall size and parameters that define major and minor axis.

I could name several other instances where it is easier to change a couple of parameters (dado, construction holes, rabbets, toe kicks...) than to create CNC code with CAM and transfer it to the machine.

Your statement is applicable to your business and your situation. I know you are making curved moldings and it makes sense to draw in CAD, load drawing in CAM and output CNC to the machine. I did the same thing with carvings, but not with things that I mentioned above.

From contributor C:
I am a former Woodwop user. We replaced Woodwop with Alphacam. Our process is 3D modeling in Acad and then Smartlister to create the dxf files for batch import into Alphacam. I never have to touch the dxf files anymore. I am mentioning this because the owner of Smartlister called me and asked questions about Woodwop. He is currently working on a feature recognition module for Woodwop. If I were you, I would give him a call. If his Woodwop dxf export works half as good as the Alphacam one, you will save so much time you will not believe it.

From the original questioner:
I'll look into it. I've just installed Autocad 2006 on my home machine, so I'll have a bash at learning a bit more of that and then persuade them to buy it at work.

From contributor M:
First things first - get rid of those stupid sample .mpr files. Most are in German anyway. WoodWop 4.5 is by far the best and most user friendly software available on CNC machining centers. These other replies are from users of other software/machinery. Don't worry, you have the best.

I will assume you have not had any formal WoodWop training. Unless you have had formal training or direct training from an experienced operator/programmer on the job, you will probably have many more question like this. I highly recommend Stiles WoodWop programming class. It's very thorough.

Anyway, you can design shapes and curves very easily. Using a coordinate system, any number of shapes can be made. You don't need any SINs, COSINs or Tangents for this. You simply use a starting point and tell the next line segment exactly to what coordinate, or to what direction and how far to move. For curves, you tell it a starting point, ending point and a radius. I prefer to use variables and formulas as much as possible, as this makes a program parametric. Although you can use some very complex formulas and programming techniques, most programs are very simple.

You can use a variety of CAD software to import designs to WoodWop using DXF format. For complex designs and 3D programming, this is very useful. But, for desktop curves and arcs you need not go any further than WoodWOP. With a little guidance from an experienced co-worker, you should be able to make any relatively simple shapes and curves within a few minutes. WoodWOP 4.5 gives you global variables that are extremely useful.

From contributor C:
I should have stated in my first post that we do use WoodWop on a daily basis. We do not use other software or machinery. My challenge to you would be to try programming a true ellipse 5 feet wide, and 2 feet tall. From start to finish. No need for variables. Then tell me how long it took you. I can tell you that by using AutoCAD, and the BPP software, it would take me less than 5 minutes to program it. That's where the challenge is. Time is money.

From contributor M:
Like I tell new operators who say "I want to make a program", You must know what you are programming. You don't just stand in front of the computer and play around. If you know what you are programming and have a blueprint, either mental or physical, it doesn't take long at all to program.

Of course, CAD programs can save you much time. I use AutoCad 2004 and the BPP for my own pleasures but have not needed it for any machining for our customers' jobs. Companies that don't already have AutoCad shouldn't have to buy it just to make complex shapes. That is why WoodWOP is so popular. Not all companies can even afford it. I have yet in many years to find a product that 100% requires a CAD program to design. Keep in mind, every company markets, designs, and manufactures their products differently. You might be able to create a design in AutoCAD just as quick as someone can create the program in WW. It depends on the operator/programmer. Unless you produce high-end custom cabinetry, AutoCAD is not a necessity, but very helpful.

And yes, even an ellipse can be created in just a couple of minutes. I have already had to do the brain work, so with the correct programming technique I have developed all full-parametric programs. I would never think of even opening a new program. Copy a similar program if it saves you 15 minutes or even 15 seconds. You can do it too!

From the original questioner:
I've had a go at making several shaped tops, but still can't help thinking there must be a more accurate way of creating tops such as wavy lengths and tops with constantly variable curves. Also, having a bit of trouble with tops that have a straight which runs into a curve, which has to be perfectly smooth. Is Autocad the way forward for this? When only specifying start and end point coordinates, it is hard to get the curve to blend into the straight, and even harder when there is no specific start and end coordinate supplied with the guesstimate drawings that customers send us. As you well know, us guessing will always end up with the customer not being happy with the shape of the curve, etc. You all know the score.

From contributor B:
Draw it in AutoCad... 5 to 15 minutes. Apply a toolpath with a CAM package... 1 to 5 minutes. Take the G-code to the router and cut the part.

Hope I don't insult anyone with such a blunt response, but I just can't see any more accurate or faster way to make one of a kind variable shape parts.

From the original questioner:
It looks like I'll be arranging an evening course in AutoCAD in September.